The invention relates to a digital demodulator and more specifically concerns a digital demodulator that will convert pulse code modulated (PCM) data from phase-shift-key (PSK) to non-return-to-zero (NRZ-L) and bi-phase (Bi.phi.-L) data.
One of the experiments being developed by the National Aeronautics and Space Administration for the Long Duration Exposure Facility is the Shuttle Bay Environment Measurements. The data gathered by this experiment is pulse code modulated for recording on magnetic tape. During different data-taking periods, the recorder is run at different speeds. In order to be compatible with the changing bandwidth of the recorder, the data is allowed to digitally phase shift key a square wave carrier having three selectable frequencies. To test the SBEM experiment, a PCM demodulator is needed to convert the data from PSK to Bi.phi.-L for decommutation and display.
It is therefore an object of this invention to provide a simple, inexpensive digital demodulator for converting pulse code modulated data from PSK to Bi.phi.-L.
Another object of this invention is to provide a digital demodulator for converting pulse code modulated data from PSK to NRZ-L.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings.